Re: [ft-devel] gamma correction and FreeType

[Søren Sandmann]

Søren Sandmann <address@hidden> writes:

> Suppose you have a checkerboard pattern where the squares are 25% and
> 75% luminance (ie., measured in linear light) respectively. Then
> consider two extremes:
>
> 1. The squares are so tiny that they are impossible to distinguish. In
>    this case the pattern will look like a solid 50% luminance, which
>    corresponds to 186 in sRGB.
>
> 2. The squares are so big that you can easily see them. In this case, if
>    you had to choose one color to represent the whole pattern, you
>    should pick the one that minimizes the overall perceptual error, for
>    example by converting to sRGB, which is roughly perceptually uniform,
>    and taking the average, producing an sRGB color of 118.

Looks like I botched the math here. In case 2, the resulting sRGB color
would be 179, so there is not that much difference for these values.

The point remains though. Using using 0% and 100%, the difference is
bigger: 186 in case 1, and 128 in case 2.


Søren